U.S. patent application number 11/651901 was filed with the patent office on 2007-05-17 for sampling circuit apparatus and method.
Invention is credited to Charles Krinke, Steven A. Moore, Roger Rauvola, John Santhoff.
Application Number | 20070110204 11/651901 |
Document ID | / |
Family ID | 34104607 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070110204 |
Kind Code |
A1 |
Santhoff; John ; et
al. |
May 17, 2007 |
Sampling circuit apparatus and method
Abstract
A system, method and apparatus for sampling an electromagnetic
signal is provided. In one embodiment of the present invention,
data is obtained from an electromagnetic signal by sampling the
received signal and demodulating the signal without mixing the
signal with a second electromagnetic signal. One feature of the
present invention is that the signal may be sampled at a rate
ranging between about 10 pico-seconds to about 500 pico-seconds.
This Abstract is provided for the sole purpose of complying with
the Abstract requirement rules that allow a reader to quickly
ascertain the subject matter of the disclosure contained herein.
This Abstract is submitted with the explicit understanding that it
will not be used to interpret or to limit the scope or the meaning
of the claims.
Inventors: |
Santhoff; John; (San Diego,
CA) ; Moore; Steven A.; (Escondido, CA) ;
Rauvola; Roger; (San Diego, CA) ; Krinke;
Charles; (Irvine, CA) |
Correspondence
Address: |
PULSE-LINK, INC.
1969 KELLOGG AVENUE
CARLSBAD
CA
92008
US
|
Family ID: |
34104607 |
Appl. No.: |
11/651901 |
Filed: |
January 9, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10633608 |
Jul 31, 2003 |
|
|
|
11651901 |
Jan 9, 2007 |
|
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Current U.S.
Class: |
375/355 |
Current CPC
Class: |
H04B 1/7183 20130101;
H04B 2201/7071 20130101; H04B 1/71637 20130101 |
Class at
Publication: |
375/355 |
International
Class: |
H04L 7/00 20060101
H04L007/00 |
Claims
1. A method of maintaining an electromagnetic signal time
reference, the method comprising the steps of: receiving the
electromagnetic signal having a first synchronization sequence;
setting a time reference based on the first synchronization
sequence; and updating the time reference before receiving a second
synchronization sequence.
2. The method of claim 1, wherein the step of updating the time
reference before receiving the second synchronization sequence
comprises the steps of: sampling the electromagnetic signal at
least twice; calculating a time reference drift of the received
signal based on the two samples; and shifting the time
reference.
3. The method of claim 2, wherein the step of sampling the
electromagnetic signal comprises sampling the electromagnetic
signal at a sample rate ranging between about 10 pico-seconds to
about 500 pico-seconds.
4. The method of claim 1, wherein the electromagnetic signal is a
communication signal selected from a group consisting of: a
substantially continuous sinusoidal signal, a plurality of
electromagnetic pulses, an ultra-wideband signal, a sinusoidal
carrier waveform, a spread spectrum signal, an analog signal, and a
digital signal.
5. The method of claim 1, wherein the electromagnetic signal is a
communication signal comprising a plurality of ultra-wideband
pulses that each have a duration ranging from about 10 picoseconds
to about 100 milliseconds.
6. The method of claim 1, wherein the electromagnetic signal is
obtained from a medium selected from a group consisting of: a
wireless medium, and a wire medium.
Description
[0001] This application claims priority under 35 U.S.C. .sctn. 120
and .sctn. 121 as a divisional of United States non-provisional
patent application Ser. No. 10/633,608, filed Jul. 31, 2003,
entitled "Sampling Circuit Apparatus and Method."
FIELD OF THE INVENTION
[0002] The present invention generally relates to electrical
circuits. More specifically, it relates to sampling and generating
electromagnetic signals.
BACKGROUND OF THE INVENTION
[0003] The wireless device industry has recently seen unprecedented
growth. With the growth of this industry, communication between
wireless devices has become increasingly important. There are a
number of different technologies for inter-device communications.
Radio frequency (RF) technology has been the predominant technology
for wireless device communications. Electro-optical devices have
also been used in wireless communications. However, electro-optical
technology suffers from low ranges and a strict need for line of
sight. RF devices therefore provide significant advantages over
electro-optical devices.
[0004] Conventional RF technology employs continuous sine waves
that are transmitted with data embedded in the modulation of the
sine waves' amplitude or frequency. For example, a conventional
cellular phone must operate at a particular frequency band of a
particular width in the total frequency spectrum. Specifically, in
the United States, the Federal Communications Commission has
allocated cellular phone communications in the 800 to 900 MHz band.
Generally, cellular phone operators divide the allocated band into
25 MHz portions, with selected portions transmitting cellular phone
signals, and other portions receiving cellular phone signals.
[0005] Another type of inter-device communication technology is
ultra-wideband (UWB). UWB wireless technology is fundamentally
different from conventional forms of RF technology. UWB employs a
"carrier free" architecture, which generally does not require the
use of high frequency carrier generation hardware; carrier
modulation hardware; frequency and phase discrimination hardware or
other devices employed in conventional frequency domain (i.e., RF)
communication systems.
[0006] A number of architectures for use of ultra-wideband
communications have been suggested. In one approach, the frequency
spectrum allocated to UWB communications devices is partitioned
into discrete bands. Modulation techniques and wireless
channelization schemes can then be designed around a UWB device
operating within one or more of these sub-bands. Alternatively, a
UWB communications device may occupy all or substantially all of
the entire allocated spectrum.
[0007] Regardless of the amount of spectrum employed, most UWB
communication devices may then use a modulation technique. For
example, a UWB device may generate UWB pulses at specific
amplitudes and or phases. All of these approaches require a UWB
device to generate specific types of pulses, or pulse morphology,
to conform to the desired architecture, or modulation
technique.
[0008] Therefore, there exists a need for an electronic circuit
architecture capable of operating in both narrowband and
ultra-wideband communications technologies.
SUMMARY OF THE INVENTION
[0009] The present invention provides circuits, systems and methods
for constructing and using an electronic circuit. In one
embodiment, the electronic circuit may be employed as a software
definable radio receiver. In this embodiment, a software
controllable sampler samples an electronic communication signal at
extremely short time intervals. The samples may then be combined to
form a received communication signal.
[0010] One feature of the present invention is to provide
demodulation and data recovery of a wide range of communication
signals, such as conventional sinusoidal waveform signals, as well
as ultra-wideband signals. An associated feature of the present
invention is that a device employing the present invention may
receive one form of communication technology (sinusoidal waveform
signals, for example) and transmit using another form of
communication technology (ultra-wideband, for example).
[0011] Another embodiment of the present invention provides a
method of maintaining time synchronization throughout extended time
periods by sampling the electromagnetic signal(s) and adjusting a
time reference based on the samples.
[0012] These and other features and advantages of the present
invention will be appreciated from review of the following detailed
description of the invention, along with the accompanying figures
in which like reference numerals refer to like parts
throughout.
BRIEF DESCRIPTION OF THE DRAWING
[0013] FIG. 1 is an illustration of different communication
methods;
[0014] FIG. 2 is an illustration of two ultra-wideband pulses;
[0015] FIG. 3 shows a schematic diagram of a programmable pulse
generator constructed according to one embodiment of the present
invention;
[0016] FIG. 4 shows a schematic diagram of a programmable pulse
generator employing a demultiplexer constructed according to
another embodiment of the present invention;
[0017] FIG. 5 shows a schematic diagram of a programmable pulse
generator constructed according to yet another embodiment of the
present invention;
[0018] FIG. 6 shows a schematic diagram of a programmable pulse
generator constructed according to another embodiment of the
present invention;
[0019] FIG. 7 shows a schematic diagram of a programmable pulse
generator constructed according to another embodiment of the
present invention;
[0020] FIG. 8 shows a schematic diagram of two series-connected
arrays of pulse generation cells constructed according to one
embodiment of the present invention;
[0021] FIG. 9 shows a schematic diagram of a two parallel-connected
arrays of pulse generation cells constructed according to another
embodiment of the present invention;
[0022] FIG. 10 shows a schematic diagram of a parallel-connected
cell arrays with an arithmetic combining circuit constructed
according to one embodiment of the present invention;
[0023] FIG. 11 shows one aggregate output of the pulse generation
cells and/or arrays of the present invention arranged to form a
electromagnetic waveform;
[0024] FIG. 12 shows different electromagnetic pulses employed in a
multi-band ultra-wideband communication system;
[0025] FIG. 13 shows the frequency space occupied by the
electromagnetic pulses in FIG. 12;
[0026] FIG. 14 shows different electromagnetic pulses formed by the
electromagnetic pulses generation cells and/or arrays of the
present invention;
[0027] FIG. 15 shows drift correction of a master time reference
according to one embodiment of the present invention; and.
[0028] FIG. 16. a electronic sampling circuit constructed according
to one embodiment of the present invention.
[0029] It will be recognized that some or all of the Figures are
schematic representations for purposes of illustration and do not
necessarily depict the actual relative sizes or locations of the
elements shown.
DETAILED DESCRIPTION OF THE INVENTION
[0030] In the following paragraphs, the present invention will be
described in detail by way of example with reference to the
attached drawings. Throughout this description, the preferred
embodiment and examples shown should be considered as exemplars,
rather than as limitations on the present invention. As used
herein, the "present invention" refers to any one of the
embodiments of the invention described herein, and any equivalents.
Furthermore, reference to various feature(s) of the "present
invention" throughout this document does not mean that all claimed
embodiments or methods must include the referenced feature(s).
[0031] There are many useful applications for extremely short
duration-pulses of electromagnetic energy. For example, in RADAR
and other imaging applications short electromagnetic pulse
durations can improve the resolution capability of the system. In
ultra-wideband communications extremely short duration pulses are
desirable as well.
[0032] The present invention provides an apparatus, method and
system for electromagnetic pulse generation having extremely short
duration. In addition, these same electromagnetic pulse generation
apparatus may be modified to function as extremely fast sampling
circuits, or cells. By sampling a received signal at an extremely
fast rate, embodiments of the present invention may function as a
receiver, and software defined radio transmitter.
[0033] In one embodiment of the present invention, a number of
extremely short duration pulse generation cells are aggregated into
an array. The aggregation may involve serial aggregation of control
inputs, serial aggregation of pulse generation cell outputs, as
well as parallel aggregation of both control inputs and pulse
generation cell outputs. The data inputs, control inputs, and the
on/off state of the current sources may be under digital computer
software control through the use of a microprocessor or a finite
state machine:
[0034] Conventional radio frequency technology employs continuous
sine waves that are transmitted with data embedded in the
modulation of the sine waves' amplitude or frequency. For example,
a conventional cellular phone must operate at a particular
frequency band of a particular width in the total frequency
spectrum. Specifically, in the United States, the Federal
Communications Commission has allocated cellular phone
communications in the 800 to 900 MHz band. Cellular phone operators
use 25 MHz of the allocated band to transmit cellular phone
signals, and another 25 MHz of the allocated band to receive
cellular phone signals.
[0035] Another example of a conventional radio frequency technology
is illustrated in FIG. 1. 802.11a, a wireless local area network
(LAN) protocol, transmits radio frequency signals at a 5 GHz center
frequency, with a radio frequency spread of about 5 MHz.
[0036] In contrast to conventional "carrier wave" communications,
another type of communication technology is emerging. Known as
ultra-wideband (UWB), or impulse radio, it employs pulses of
electromagnetic energy that are emitted at nanosecond or picosecond
intervals (generally tens of picoseconds to a few nanoseconds in
duration). For this reason, ultra-wideband is often called "impulse
radio." Because the excitation pulse is not a modulated waveform,
UWB has also been termed "carrier-free" in that no apparent carrier
frequency is evident in the radio frequency (RF) spectrum. That is,
the UWB pulses are transmitted without modulation onto a sine wave
carrier frequency, in contrast with conventional radio frequency
technology. Ultra-wideband requires neither an assigned frequency,
a power amplifier, high frequency carrier generation hardware,
carrier modulation hardware, stabilizers, frequency and phase
discrimination hardware or other devices employed in conventional
frequency domain communication systems.
[0037] Referring to FIG. 2, an ultra-wideband (UWB) pulse may have
a 1.8 GHz center frequency, with a frequency spread of
approximately 3.2 GHz, which illustrates two typical UWB pulses.
FIG. 2 illustrates that the narrower the UWB pulse in time, the
broader the spread of its frequency spectrum. This is because
frequency is inversely proportional to the time duration of the
pulse. A 600-picosecond UWB pulse can have about a 1.8 GHz center
frequency, with a frequency spread of approximately 1.6 GHz. And a
300-picosecond UWB pulse can have about a 3 GHz center frequency,
with a frequency spread of approximately 3.2 GHz. And, a
50-picosecond UWB pulse can have about a 10 GHz center frequency,
with a frequency spread of approximately 20 GHz. As mentioned
above, the present invention is capable of producing extremely
short duration electromagnetic pulses. For example, the present
invention may produce electromagnetic pulses having a duration of
as little as 1 picosecond.
[0038] Thus, UWB pulses generally do not operate within a specific
frequency, as shown in FIG. 1. And because UWB pulses are spread
across an extremely wide frequency range, UWB communication systems
allow communications at very high data rates, such as 100 megabits
per second or greater.
[0039] Further details of UWB technology are disclosed in U.S. Pat.
3,728,632 (in the name of Gerald F. Ross, and titled: Transmission
and Reception System for Generating and Receiving Base-Band
Duration Pulse Signals without Distortion for Short Base-Band Pulse
Communication System), which is referred to and incorporated herein
in its entirety by this reference.
[0040] Also, because the UWB pulse is spread across an extremely
wide frequency range, the power sampled at a single, or specific
frequency is very low. For example, a UWB one-watt signal of one
nano-second duration spreads the one-watt over the entire frequency
occupied by the pulse. At any single frequency, such as a cellular
phone carrier frequency, the UWB pulse power present is one
nano-watt (for a frequency band of 1 GHz). This is well within the
noise floor of any cellular phone system and therefore does not
interfere with the demodulation and recovery of the original
cellular phone signals. Generally, the UWB pulses are transmitted
at relatively low power (when sampled at a single, or specific
frequency), for example, at less than -30 power decibels to -60
power decibels, which minimizes interference with conventional
radio frequencies.
[0041] As described above, conventional wireless devices
communicate with Radio Frequency (RF) energy. Conventional
technologies for RF communications employ RF carrier waves. Data is
modulated onto the carrier wave, amplified and transmitted from a
RF device. A second RF wireless device receives the carrier wave,
amplifies the wave, and demodulates the data. RF communications
suffer from fading, multi-path interference, and channel
attenuation. Since RF energy strength is proportional to the
inverse of the transmitted distance squared, the quality of RF
wireless communication is dependent on the relative location of the
RF devices that are communicating. Atmospheric conditions, terrain,
natural and man-made objects can additionally degrade the received
signal strength of RF communications
[0042] One feature of the present invention is that with extremely
short electromagnetic pulse generation capability, software-defined
radio becomes feasible. That is, a conventional radio transmitter
generally comprises a carrier-wave generator constructed to
transmit a specific radio frequency, a device for modulating the
carrier wave in accordance with information to be broadcast,
amplifiers and an aerial system. This conventional radio
transmitter only transmits at a specific frequency.
[0043] Software-defined radio is communication in which
electromagnetic pulses, or conventional sine waveforms are
generated, modulated, and decoded only by computer software. This
allows a single computer-controlled receiver, transmitter or
transceiver to interface and operate with a variety of
communication services that use different frequencies, modulation
methods and/or protocols. Changing the frequency, modulation method
and/or protocol only requires using a different computer software
program. Thus, software-defined radio is much more economical to
manufacture, package, and produce.
[0044] Another embodiment of the present invention provides a
method of maintaining signal time synchronization throughout
extended time periods by sampling the electromagnetic signal(s) and
adjusting a time reference based on the samples. This reduces, or
eliminates, the dependency on phase locked loop circuits and the
increased overhead of re-synchronization.
[0045] One feature of the present invention is that a group of
short duration pulses of electromagnetic energy can be aggregated,
or "stacked-up" to form a conventional radio frequency signal. A
communication signal sampling theorem states that a signal must be
sampled at twice the highest frequency component to be reliably
recovered. This signal sampling theorem is generally known as
either the Nyquist sampling theorem or the Shannon sampling
theorem.
[0046] One corollary of this sampling theorem is that
electromagnetic pulse generation systems can be used to represent,
or simulate, continuous waveform signals if the time resolution, or
duration of the pulses is such that the inverse of resolution is at
least twice the highest frequency component in the desired
waveform. For example, to aggregate a pulsed signal to represent
cellular communications at 900 MHz would require at a minimum a 555
pico-second pulse duration. To replicate a 802.11(a) (i.e.,
BLUETOOTH) waveform would require pulse durations of 100
pico-seconds or less since the center frequency assigned to that
communications technology is approximately 5 GHz. Additionally, to
represent some conventional signal modulation techniques, the
amplitude of the carrier waveform must also be reliably
constructed. Therefore, re-creation, or simulation, of an amplitude
modulated waveform may require the capability to produce extremely
short duration pulses while controlling the amplitude of the
pulses.
[0047] One capability envisioned by the present invention is a
single mobile, or fixed, wireless device that can switch between
various wireless, or wire communication technologies and standards.
By way of example and not limitation, a device constructed
according to the present invention may communicate with BLUETOOTH,
WiFi, UWB, CDMA, GSM, PCS and a host of other communication
technologies by employing a software-defined radio. One feature of
the present invention is the generation and aggregation of
extremely short duration electromagnetic pulses into waveforms that
simulate a wide range of wireless communication technologies.
[0048] Wireless communication technologies may use a number of
modulation techniques to impart data to the signal prior to
transmission. Most of these modulation techniques are imparted to
an existing carrier signal that changes properties based on the
data. For example, in phase modulation schemes the phase of a
carrier waveform is shifted in increments depending of the data to
be imparted. In Amplitude Modulation (AM) the amplitude of the
carrier signal is varied by the data to be carried. In Orthogonal
Frequency Division Modulation (OFDM) data is modulated onto a set
of orthogonal carriers prior to transmission. Since the carriers
are selected to be orthogonal, there is minimal interference
between the resultant modulated signals.
[0049] Ultra-wideband (UWB) pulse modulation techniques enable a
single representative data symbol to represent a plurality of
binary digits, or bits. This has the obvious advantage of
increasing the data rate in a communication system. A few examples
of UWB modulation include Pulse Width Modulation (PWM), Pulse
Amplitude Modulation (PAM), and Pulse Position Modulation (PPM). In
PWM, a series of pre-defined UWB pulse widths are used to represent
different sets of bits. For example, in a system employing 8
different UWB pulse widths, each symbol could represent one of 8
combinations. This symbol would carry 3 bits of information. In
PAM, pre-defined UWB pulse amplitudes are used to represent
different sets of bits. A system employing PAM16 would have 16
pre-defined UWB pulse amplitudes. This system would be able to
carry 4 bits of information per symbol. In a PPM system,
pre-defined positions within an UWB pulse timeslot are used to
carry a set of bits. A system employing PPM16 would be capable of
carrying 4 bits of information per symbol. Additional UWB pulse
modulation techniques, not listed, may be employed by the present
invention.
[0050] One feature of the present invention is that it allows a
computer software control unit to select appropriate
electromagnetic pulse generation cells in such a way as to generate
a carrier signal that is already modulated to reflect the desired
data to be sent. This can reduce the complexity and expense of
communication device design in that modulation hardware is no
longer necessary to impart data onto the carrier signal.
[0051] An additional feature of the present invention is that it
may act as a "bridge" between different communication technologies.
By way of example and not limitation, a narrowband PCS signal may
be received at a frequency of approximately 1.9 GHz. A
communication device employing the present invention may
re-transmit the PCS signal by transmitting a 900 MHz signal that
conforms with a CDMA communication system. Alternatively, the
re-transmission may employ a UWB wireless link using UWB
communication methods described above. The UWB wireless link may
transmit across a frequency band extending from about 3.1 GHz to
about 10.6 GHz.
[0052] The present invention provides a computer software
controllable waveform generator for use in wireless, or wire
communication that aggregates a number of extremely short duration
pulses. Further details of extremely short electromagnetic pulse
generation techniques and methods are discussed in detail in
METHODS, APPARATUSES, AND SYSTEMS FOR SAMPLING OR PULSE GENERATION,
U.S. Pat. No. 6,433,720, issued to Libove et al., on Aug. 13, 2002,
which is incorporated herein by reference in its entirety.
[0053] The electromagnetic pulse generation cell(s) employed in the
present invention may have one, or more software controllable
interfaces. In one embodiment, the software control interface
employs at least one digital to analog conversion (DAC) circuit. In
this embodiment, a DAC may be used to provide the control signal of
the pulse generation cell(s). Alternatively, a DAC may be used to
deactivate a switch placed inline with the current source of each
pulse generation cell effectively shutting down unused pulse
generation cell(s). Alternatively, a DAC may be used by a software
control unit to control the flow of data to the input stage of each
pulse generation cell. A still further use of a software controlled
DAC would provide control signals to the aggregation or combining
circuit that combines the output of serial and/or parallel arrays
of pulse generation cells. Additionally a DAC may be used to
provide threshold voltage levels in the pulse generation
cell(s).
[0054] In another embodiment of the present invention, a computer
microprocessor or alternatively a finite state machine, may send
signals directly to the above mentioned inputs without the use of
DAC hardware. A finite state machine is any device that stores the
status of something at a given time and can operate on input to
change the status and/or cause an action or output to take place
for any given change. Thus, at any given moment in time, a computer
system can be seen as a set of states and each program in it as a
finite state machine. For example, a finite state machine may be a
hardware implementation of computer logic, or software.
[0055] As conceived herein, electromagnetic pulse generation cells
may be configured in a number of ways. In one embodiment, pulse
generation cells are connected in series, relative to the control
input, with a single set of output terminals to form a Serial Array
Single Output (SASO). In this embodiment delay lines may be used to
set the time of pulse generation of each cell relative to the first
cell's output. Generally, a delay line is a device that introduces
a time lag in a signal. The time lag is usually calculated as the
time required for the signal to pass though the delay line device,
minus the time necessary for the signal to traverse the same
distance without the delay line.
[0056] In this configuration, a transition in a control signal
generates a pulse proportional to the data input on the first cell.
The control signal then passes through a delay line to a second
cell and causes a pulse to be generated in the output proportional
to the data input on the second cell. The second pulse is delayed
in time relative to the first by the delay in the control signal.
Subsequent stages in the SASO can be further delayed providing
pulse outputs at their appropriate time interval. This
configuration may be used without delay lines causing the pulses
produced by each individual cell to be summed at the output
terminals.
[0057] Another configuration of pulse generation cells involves
connecting in series, relative to the control input, a number of
cells where each cell has output terminals. In this configuration,
a serial input multiple output (SAMO), can be implemented with or
without delay lines to provide simultaneous outputs or outputs that
are temporally spaced due to the delay in the control transition.
In this configuration, the outputs may be summed at a common node,
or provided to a mixing circuit such as a Gilbert Multiplier, or a
Half Gilbert Multiplier, and the product is then taken.
[0058] In a still further configuration, a combination of
electromagnetic pulse generation cells may be connected in
parallel, relative to the control inputs. In this configuration,
each pulse generation cell may receive a different control signal.
In this configuration, the timing of the control inputs can
directly control generation and temporal spacing of the pulses. The
cells may be configured to have a single output (PASO) or multiple
outputs (PAMO).
[0059] In another configuration, two-dimensional arrays of SASO,
SAMO, PASO, and PAMO arrays may be connected serially or in
parallel to provide additional functionality.
[0060] In conventional communication technologies a carrier
waveform is generated then data is modulated onto the waveform. For
example, most conventional systems use a local oscillator to
provide a sine wave carrier, and then data is modulated onto the
carrier, or waveform. In some forms of ultra-wideband
communications, a pulse is generated then filtered or mixed to
achieve a desired center frequency. In one embodiment of the
present invention, the pulse generation cells are configured to
produce waveforms at the desired center frequency, and are also
configured to represent data in its modulated form. This reduces
the complexity and expense of the transmitter design by eliminating
modulation and mixing hardware and potentially eliminating the need
for bandpass filters.
[0061] By controlling the shape of a generated waveform to the tens
of picoseconds, it is possible to limit the frequency content of
the resultant waveform. One feature of the present invention
provides a waveform generator for electronic communication systems
that complies with FCC emission limit regulations without employing
bandpass filters to reject out-of-band emissions.
[0062] Another feature of the present invention provides a waveform
generator that may be software controlled to produce ultra-wideband
(UWB) pulses compliant with both single-band and multi-band UWB
systems. Current Federal Communications Commission (FCC)
regulations establish "spectrum masks" that limit outdoor
ultra-wideband emissions to -41 dBm between 3.1 GHz and 10.6 GHz. A
single-band ultra-wideband (UWB) communication system may emit UWB
pulses having a frequency spread that would extend from about 3.1
GHz to about 10.6 GHz. A multi-band UWB communication system may
break-up the available frequency and emit UWB pulses in discrete
frequency bands, for example, 200 MHz bands, 400 MHz bands, or 600
MHz bands. It will be appreciated that other frequency band
allocations may be employed. An example of a possible multi-band
UWB communication system is illustrated in FIG. 10.
[0063] Additionally, the present invention allows a communication
device to bridge, or convert data received from a single-band UWB
communication system to a multi-band communication system and
vice-versa, as well as bridging data between conventional carrier
wave communication technologies as described above, and UWB
communication technologies.
[0064] Referring now to FIG. 3, an electromagnetic pulse generation
cell constructed according to one embodiment of the present
invention is illustrated. This electromagnetic pulse generation
cell, as well as the other embodiment electromagnetic pulse
generation cells described herein, may be employed as extremely
fast electromagnetic sampling cells, or circuits as well. For
example, a signal to be sampled is superimposed on the inputs to
the first differentially paired transistors (DPTs), described
below. When the circuit, or cell, is in the active mode (that is,
when the DPTs are in the triode region between on and off) the
output pulse is proportional to the signal present on the inputs.
In this manner these circuits, or cells, are capable of sampling an
incoming electromagnetic signal at a time resolution equivalent to
the pulse generation aperture.
[0065] For example, a number of communications systems employ some
form of signal amplitude modulation (AM). There are various
approaches to demodulate AM signals. In one approach, an AM signal
is mixed with a carrier at the same frequency. The AM signal can be
represented by y(t)=m(t)cos (.omega..sub.ct), where m(t) is the
data present on carrier cos (.omega..sub.c). Mixing this signal
with a carrier at (.omega..sub.c), yields the following: x
.function. ( t ) = y .function. ( t ) .times. .times. cos
.function. ( .omega. c .times. t ) ##EQU1## x .function. ( t ) = m
.function. ( t ) .times. .times. cos .function. ( .omega. c .times.
t ) .times. .times. cos .function. ( .omega. c .times. t )
##EQU1.2## x .function. ( t ) = m .function. ( t ) .times. .times.
cos 2 .function. ( .omega. c .times. t ) ##EQU1.3## x .function. (
t ) = 1 2 .times. m .function. ( t ) + 1 2 .times. cos .function. (
2 .times. .omega. c .times. t ) ##EQU1.4##
[0066] The resultant signal is then filtered with a lowpass filter
that recovers the 1 2 .times. m .function. ( t ) ##EQU2## component
of the signal. Another demodulation method employs an envelope
detector and an analog to digital converter.
[0067] In contrast, the present invention uses extremely fast
sampling cells, as described below, whose output is proportional to
the amplitude of the signal received. Direct demodulation of AM
signals is therefore possible without the use of mixers or envelope
detectors that are traditionally used.
[0068] Similarly, in frequency modulated (FM) and phase modulated
communications systems the data is carried in the instantaneous
frequency of the signal. Demodulation of these two types of signals
is similar in nature. Demodulation of FM is usually accomplished
using a phase locked loop (PLL) circuit and mixing circuits. The
present invention, sampling at extremely fast rates, can detect
variations in phase and frequency directly from the output of the
sampling cells by a mathematical combining circuit.
[0069] Referring now to FIG. 3, an electromagnetic pulse
generation, or sampling cell constructed according to one
embodiment of the present invention is illustrated. Data of
interest is input to the gate terminals (G) of the differential
input stage DPT 1. DPT 1 has its source terminals (S) connected to
the current source. The drain terminals (D) of DPT 1 are connected
to the source terminals (S) of DPT 2. The gate terminals (G) of DPT
2 are connected to the output of the Inverter. The Inverter may be
a phase inverter, a digital inverter, or any other suitable
inverter.
[0070] The drain terminals (D) of DPT 2 are connected to the source
terminals (S) of DPT 3. The gate terminals (G) of DPT 3 are
connected to the output of a delay element D1. As discussed above,
the delay element is a device that introduces a time lag in a
signal. The time lag is usually calculated as the time required for
the signal to pass though the delay line device, minus the time
necessary for the signal to traverse the same distance without the
delay element.
[0071] The drain terminals (D) of DPT 3 are connected to resistive
elements R1 and R2. Resistive elements R3 and R4 are connected to a
voltage source such as Vdd and to the source terminals (S) of DPT
3.
[0072] A Control signal is connected to the input of delay D1 and
to the input of the Inverter. The power and ground connections of
the Inverter can be connected to Vddl and Vss respectively, or
alternatively to other voltage potentials not shown. All of the
signals may be software controlled by the use of a software control
unit (SCU), and/or optional digital to analog converters (DACs) not
shown. DAC circuits may comprise multi-bit DAC circuits or
alternatively be replaced by voltage divider circuits configured to
provide specific voltage levels used by the pulse generation
cell.
[0073] The Control may comprise a SCU or one or more DACs, and
generate the control signals. The delay element D1 is calculated to
delay the Control signal from reaching the gate terminals (G) of
DPT 3 until the output of the Inverter reaches the gate terminals
(G) of DPT 2. Alternatively, the Inverter may be connected to a
voltage level distinct from Vddl.
[0074] The function of resistive elements R3 and R4 is to provide
appropriate biasing to the circuit. For example, as is generally
known, biasing is used to establish a predetermined threshold or
operating point. Other methods of biasing are known in the art and
may be used to provide this function.
[0075] The operation of the electromagnetic pulse generation cell
illustrated in FIG. 3 will now be explained. When Control is at a
low voltage level, DPT 3 is turned "off" and the output of the
Inverter turns "on" DPT 2. When Control is at a high voltage level,
DPT 3 is turned "on" and the output of the Inverter turns "off" DPT
2. During the transition of Control from a first voltage level to a
second voltage level, both DPT 3 and DPT 2 allow current to flow.
Because the amount of current is dependent on the voltage levels at
the input terminals of DPT 1, the output signal will be
proportional to the voltage present at those terminals.
[0076] Referring now to FIG. 4, an alternative embodiment
electromagnetic pulse generation cell, similar to the cell of FIG.
3 is illustrated. The pulse generation cell of FIG. 4 includes a
demultiplexer. Another embodiment of an electromagnetic pulse
generation cell may be configured as illustrated in FIG. 4, but may
also include the DAC circuits 20(a-g) illustrated in FIG. 3. The
embodiment illustrated in FIG. 4 is essentially constructed as
illustrated and described above in connection with FIG. 3, with the
exception that all signals from the SCU are sent to demultiplexer
50. Demultiplexer 50 is under the control of SCU 10. Control and
data signals are sent to demultiplexer 50 from SCU 10. In this
embodiment, the demultiplexer 50 routes the appropriate signals to
the different parts of the pulse generation circuit illustrated in
FIG. 4.
[0077] Referring now to FIG. 5, an electromagnetic pulse generation
cell constructed according to one embodiment of the present
invention is illustrated. Data is input to the gate terminals (G)
of the differential input stage DPT 1. DPT 1 has its source
terminals (S) connected to the current source. The drain terminals
(D) of DPT 1 are connected to the source terminals (S) of DPT 2.
The gate terminals (G) of DPT 2 are connected to the output of the
Inverter. The Inverter may be a phase inverter, a digital inverter,
or any other suitable inverter.
[0078] The drain terminals (D) of DPT 2 are connected to the source
terminals (S) of DPT 3. The gate terminals (G) of DPT 3 are
connected to the output of a delay element D1. As discussed above,
the delay element is a device that introduces a time lag in a
signal. The time lag is usually calculated as the time required for
the signal to pass though the delay line device, minus the time
necessary for the signal to traverse the same distance without the
delay element.
[0079] The drain terminals (D) of DPT 3 are connected to resistive
elements R1 and R2. Resistive elements R3 and R4 are connected to a
voltage source such as Vdd and to the source terminals (S) of DPT
3.
[0080] A Control signal is connected to the input of delay D1 and
to the input of the Inverter. The power and ground connections of
the Inverter can be connected to Vddl and Vss respectively, or
alternatively to other voltage potentials not shown. All of the
signals may be software controlled by the use of a software control
unit (SCU), and/or optional digital to analog converters (DACs) not
shown. DAC circuits may comprise multi-bit DAC circuits or
alternatively be replaced by voltage divider circuits configured to
provide specific voltage levels used by the pulse generation
cell.
[0081] The Control may comprise a SCU or one or more DACs, and
generate the control signals. The delay element D1 is calculated to
delay the Control signal from reaching the gate terminals (G) of
DPT 3 until the output of the Inverter reaches the gate terminals
(G) of DPT 2. Alternatively, the Inverter may be connected to a
voltage level distinct from Vddl.
[0082] The function of resistive elements R3 and R4 is to provide
appropriate biasing to the circuit. For example, as is generally
known, biasing is used to establish a predetermined threshold or
operating point. Other methods of biasing are known in the art and
may be used to provide this function.
[0083] The operation of the electromagnetic pulse generation cell
illustrated in FIG. 5 will now be explained. When Control is at a
low voltage level, DPT 3 is turned "off" and the output of the
Inverter turns "on" DPT 2. When Control is at a high voltage level,
DPT 3 is turned "on" and the output of the Inverter turns "off" DPT
2. During the transition of Control from a first voltage level to a
second voltage level, both DPT 3 and DPT 2 allow current to flow.
Because the amount of current is dependent on the voltage levels at
the input terminals of DPT 1, the output signal will be
proportional to the voltage present at those terminals.
[0084] Referring now to FIGS. 6 and 7, electromagnetic pulse
generation cells constructed according to other embodiments of the
present invention are illustrated. In one embodiment of this
architecture, a plurality of current sources I.sub.1 through
I.sub.n provide current through resistive elements R.sub.11 through
R.sub.n1 when switches SW.sub.1 through SW.sub.n are in the open
position. This mode of operation ensures that the current sources
I.sub.1 through I.sub.n remain turned-on prior to selection by
software control unit (SCU) 10. SCU 10 is capable of providing a
number of control signals to the cell. SCU 10 may comprise a
microprocessor or alternatively may comprise a finite state machine
capable of providing the necessary digital control signals to the
various parts of the pulse generation cells illustrated in FIGS. 4
and 5.
[0085] SCU 10 provides set-up signals SU1 through SUn to switches
SW.sub.1 through SW.sub.n. Switches SW.sub.1 through SWn are in
either an open or a closed state depending on the set-up signals
SU1 through SUn. Once selected R.sub.12 through R.sub.n2 provide a
path for currents I.sub.1 through I.sub.n prior to the Firing
Signal becoming active. In this state, SCU 10 has selected which
currents I.sub.1 through I.sub.n will pass through high-speed
switch SW.sub.(fast) when the Firing Signal is activated. Once the
Firing Signal is activated by SCU 10, the I.sub.total, the sum of
the selected currents I.sub.1 through I.sub.n, conducts through
high-speed switch SW.sub.(fast) and develops a change in voltage
V.sub.out.
[0086] In the electromagnetic pulse generation cell illustrated in
FIG. 6, the current sources I.sub.1 through I.sub.n are mirror
currents of a master current source. These mirror currents may be
precisely controlled to be near duplicates of the master current
source (not shown). Alternatively, a number of known techniques may
be employed to divide or multiply the master current source (not
shown) to obtain other current values. A number of devices may be
used as selection switches, and include transistors, differential
paired transistors (DPTs), and other suitable devices.
[0087] High-speed switch SW.sub.(fast) may only allow current to
pass when two or more switching elements, such as transistors, are
in the triode region, and prevent current flow when at least one of
the switching elements is saturated, or in an off state.
[0088] For example, when an inverter comprising at least two
transistors is used for high-speed switch SW.sub.(fast), the switch
SW.sub.(fast) is in steady-state when one transistor is off and the
other is on. The triode region (when both transistors are between
on and off) that occurs when the transistors switch states provides
a path for current flow. Specifically, the triode state occurs
between when the first transistor is on and the second transistor
is off, to when the first transistor is off and the second
transistor is on. This triode region, between when the transistors
switch states, provides a path for current flow.
[0089] In the first state, V.sub.out would approximate V.sub.ss
since no current is flowing across the load. Likewise in the second
state V.sub.out approximates V.sub.ss for the same reason. When
SW.sub.(fast) is switching states, current is allowed to flow
across the load and an electromagnetic pulse is produced.
[0090] In an alternate embodiment of this extremely short duration
electromagnetic pulse generation architecture, shown in FIG. 7,
source currents I.sub.1 through I.sub.n, are duplicated as sink
currents I'.sub.1, through I'.sub.n. Additionally, switches
SW.sub.1 through SW.sub.n are duplicated in the sink channel as
SW'.sub.1 through SW'.sub.n. In this embodiment, SCU 10 provides
set-up signals SU'1 through SU'n to switches SW'.sub.1 through
SW'.sub.n ensuring the aggregate currents sourced from I.sub.1
through I.sub.n are sinked by I'.sub.1 through I'.sub.n. That is,
I'.sub.1 through I'.sub.n provide a path to ground for I.sub.1
through I.sub.n.
[0091] The high-speed switch SW.sub.(fast) can provide a higher
impedance path for current when in the open state. When high-speed
switch SW.sub.(fast) receives a Firing Signal from SCU 10, it
changes states and allows I.sub.total, the sum of currents I.sub.1
through I'.sub.n to flow to the load R.sub.load and C.sub.1.
[0092] Referring to FIG. 8, two additional configurations of pulse
generation cells constructed according to the present invention are
illustrated. Each of Cell 1-4 represents any one of the pulse
generation cells illustrated in FIGS. 3-7, or alternative
embodiments thereof. It will be appreciated that any number of
pulse generation cells may be employed by the present invention,
with the four cells illustrated for drawing expediency. Cell array
90 is a Parallel Array Single Output (PASO). In this configuration,
data 1-4 is input into each cell 1-4, and the control inputs 1-4
are individually input into each cell 1-4. The entire cell array 90
is configured to give a single differential output. Alternatively,
cell array 100 is a Parallel Array Multiple Output array (PAMO). In
this configuration, the control inputs 1-4 are individually input
into each cell 1-4, but each cell has an independent output
1-4.
[0093] Referring to FIG. 9, two additional configurations of pulse
generation cells constructed according to the present invention are
illustrated. Each of Cell 1-4 represents any one of the pulse
generation cells illustrated in FIGS. 3-7, or alternative
embodiments thereof. It will be appreciated that any number of
pulse generation cells may be employed by the present invention,
with the four cells illustrated for drawing expediency. Cell array
90 is a Parallel Array Single Output (PASO). In this configuration,
data 1-4 is input into each cell 1-4, and the control inputs 1-4
are individually input into each cell 1-4. The entire cell array 90
is configured to give a single differential output. Alternatively,
cell array 100 is a Parallel Array Multiple Output array (PAMO). In
this configuration, the control inputs 1-4 are individually input
into each cell 1-4, but each cell has an independent output
1-4.
[0094] Referring to FIG. 10, an arithmetic combination circuit 120
is combined with a group of array elements 1-4. The output from the
arithmetic combination circuit 120 may be used to produce any
desired electromagnetic waveform. It will be appreciated that any
number of array elements may be employed by the present invention,
with the four array elements illustrated for drawing expediency.
Array elements 110(a-d) are connected in parallel to Arithmetic
Combination Circuit 120. The Array elements shown may comprise the
cell arrays 70, 80, 90 and 100 (SASO, SAMO, PASO, and PAMO) as
described above in connection with FIGS. 5-6. Any number of array
elements may be used to produce a desired electromagnetic waveform.
Data 1-4 is input into the array elements 1-4, and the outputs 1-4
of the array elements 110(a-d) are connected to arithmetic
combination circuit 120. The arithmetic combination circuit 120 may
comprise switching elements, summing circuits, inverting circuits,
integrating and differentiating circuits, mixers, multipliers, and
other suitable devices. Additionally, the arithmetic combination
circuit 120 may be computer software controllable, and may or may
not include DAC circuitry.
[0095] Referring to FIG. 10, an arithmetic combination circuit 120
is combined with a group of array elements 1-4. The output from the
arithmetic combination circuit 120 may be used to produce any
desired electromagnetic waveform. It will be appreciated that any
number of array elements may be employed by the present invention,
with the four array elements illustrated for drawing expediency.
Array elements 110(a-d) are connected in parallel to Arithmetic
Combination Circuit 120. The Array elements shown may comprise the
cell arrays 70, 80, 90 and 100 (SASO, SAMO, PASO, and PAMO) as
described above in connection with FIGS. 8-9. Any number of array
elements may be used to produce a desired electromagnetic waveform.
Data 1-4 is input into the array elements 1-4, and the outputs 1-4
of the array elements 110(a-d) are connected to arithmetic
combination circuit 120. The arithmetic combination circuit 120 may
comprise switching elements, summing circuits, inverting circuits,
integrating and differentiating circuits, mixers, multipliers, and
other suitable devices. Additionally, the arithmetic combination
circuit 120 may be computer software controllable, and may or may
not include DAC circuitry.
[0096] FIG. 11 illustrates an electromagnetic sine wave generated
by the arithmetic aggregation of outputs from the cells 1-4 or
arrays 1-4. In this example, the cell 1-4 or array 1-4 outputs
130(a-g) are summed to produce an electromagnetic sine wave as an
output 140. Each output 130(a-g), corresponding to the outputs from
the cells 1-4 or arrays 1-4, is independently controllable, as
discussed above in connection with the operation of the cells 1-4
and array elements 1-4. Thus, any desired waveform, such as
waveform 140, shown in FIG. 11, can be produced by the arithmetic
combination circuit 120.
[0097] As also shown in FIG. 11, discrete pulses of electromagnetic
energy can be output from the plurality of cells 1-4 or arrays 1-4.
These individual outputs 103(a-g), can be employed individually, or
aggregated for use in an ultra-wideband communication system, with
discrete pulses ranging from about 1 pico-second to about 1
milli-second in duration.
[0098] FIGS. 12 and 13 illustrate electromagnetic pulses generated
by the outputs from one or more cells 1-4 or arrays 1-4. In this
example, the cell 1-4 or array 1-4 outputs are in the form of a
plurality of pulses 150(a-j). Shown in FIG. 10, are the frequency
spectra 160(a-j) corresponding to each of the pulses 150(a-j).
[0099] One feature of the present invention is that pulses 150
(a-j) having frequency spectra 160 (a-j) may be used in a
multi-band ultra-wideband (UWB) communication system. For example,
multi-band UWB systems usually fall into two architectures. The
first architecture generates a electromagnetic pulse with a
duration relating to the amount of frequency to be occupied by the
band. The UWB pulse is then filtered with a bandpass filter that
has a center frequency at the center of the frequency band to be
occupied. When transmitted, the resultant pulse will occupy the
appropriate amount of frequency around the center of the bandpass
filters bandwidth.
[0100] A second multi-band UWB communication architecture involves
generating a pulse with the appropriate bandwidth and mixing it
with a carrier wave of the desired center frequency. The complexity
of both architectures is significant.
[0101] In one embodiment of the present invention, multi-band UWB
pulses are generated directly without the use of mixing circuits
and bandpass filters. These pulse streams are generated directly,
or are generated by the aggregation of pulse generation cells using
the arithmetic combination circuit 120, shown in FIG. 10. Since the
electromagnetic waveform generator herein described is controlled
by computer software, it has the ability to quickly and easily
switch between single-band UWB communication architectures and
multi-band UWB communication architectures by generating pulses
with characteristics suitable to each architecture. Additionally,
the same electromagnetic waveform generator may be used to generate
a wide range of conventional sine wave signals (140), as shown in
FIG. 11
[0102] Referring specifically to FIG. 14, in another embodiment of
the present invention narrow pulse widths can be obtained by
initially generating pulses 170(a) and 170(b). The initial pulses
170(a) and 170(b) may have duration T.sub.0. The Arithmetic
Combination Circuit 120 is used to narrow the resulting pulses to
duration T.sub.1 by delaying pulse 170(b) and by amount T.sub.1 and
performing an arithmetic function, addition in the case shown, on
the two pulses. The resultant pulses 170(c) have duration T.sub.1.
For example, the ultra-fast pulse generation cells herein described
are capable of generating pulses with durations of 50 picoseconds
or less. With the use of delay lines, pulse 170(b) can be delayed
by 10 picoseconds relative to pulse 170(a). The sum of pulses
170(a) and 170(b) shown in 170(c) would then have a duration of 10
picoseconds.
[0103] Referring to FIG. 15, a method of synchronizing, or
correcting a time reference according to one embodiment of the
present invention is illustrated. Generally, conventional
communication devices require the transmitter and the receiver to
synchronize their time references, or master time references.
Typically when the receiving device detects a time synchronization
sequence, it sets its master time reference to the timing of the
synchronization sequence. Since there is relative clock drift
between the transmitters master time reference and the receivers
master time reference, periodic resynchronization is usually
required to ensure reliable data communications and low Bit Error
Rates (BER).
[0104] In one embodiment of the present invention, extremely fast
sampling of received signals is used to update the receiver's
master time reference relative to the transmitter's master time
reference. This enables less frequent re-synchronization and can
eliminate the need for complex Phase Locked Loop (PLL) circuitry.
The reduced need for re-synchronization also lowers overhead in the
data stream and therefore increases overall data throughput of the
communication system.
[0105] For example, as shown in FIG. 15, an electromagnetic pulse
duration may have a duration of T.sub.0, or alternatively, a "time
bin" where an electromagnetic pulse may be located may have a
duration of T.sub.0. An extremely fast sampling array comprised of
the cells and circuits described herein may have resolution of
T.sub.1. With these extremely fast sampling arrays, multiple signal
samples may be obtained during time period T.sub.0. For example, if
the pulse duration is about 4 nano-seconds in duration, a 50
pico-second sampler could obtain 80 samples. As the electromagnetic
pulses, or signals are detected at times that deviate from the
master time reference of the receiver, the receiver time reference
is updated.
[0106] As illustrated in FIG. 15, an electromagnetic pulse on line
10(a) arrives at the time the receiver expects. In 10(b) the pulse
is delayed by two sampling periods. In 10(c) the receiver adjusts
its master time reference from the drift present in 10(b) and the
pulse is centered within the time period expected. In 10(d) shows
another example of "clock drift," and 10(e) shows a further
correction of the receiver master time reference due to the drift
in 10(d). Thus, the extremely fast sampling circuits, or cells of
the present invention provide a method to correct relative
deviations in master time references between transmitter and
receiver without the need for resynchronization.
[0107] Referring now to FIG. 16, which illustrates an extremely
fast sampling circuit according to one embodiment of the present
invention. A Half Gilbert Multiplier circuit receives an input
signal from a signal source, such as a receiver, antenna, or other
suitable device. The Half Gilbert Multiplier multiplies the
incoming current by a reference current. This resultant signal is
proportional to the input signal to be sampled. Software Control
Unit (SCU) sends a signal Sul to the first switch SW1. Resistors R1
and R2 provide a path for current flow when switches SW1 and
SW.sub.(fast) are in the open position. When a sample is desired of
the incoming signal the SCU sends a Firing Signal to SW(fast),
allowing current Itotal to load resistor RLoad and capacitor, or
other type of energy storage element C1. Current Itotal, flowing
across resistor RLoad and energy storage element C1, produces an
output voltage Vout that is proportional to the signal being
sampled. Energy storage element C1 additionally holds the value of
Vout for a time period defined by (RLoad)(C1).
[0108] Thus, it is seen that a system, method and article of
manufacture are provided for arbitrary waveform generation suitable
for communications in a wired or wireless medium. One skilled in
the art will appreciate that the present invention can be practiced
by other than the above-described embodiments, which are presented
in this description for purposes of illustration and not of
limitation. The description and examples set forth in this
specification and associated drawings only set forth preferred
embodiment(s) of the present invention. The specification and
drawings are not intended to limit the exclusionary scope of this
patent document. Many designs other than the above-described
embodiments will fall within the literal and/or legal scope of the
following claims, and the present invention is limited only by the
claims that follow. It is noted that various equivalents for the
particular embodiments discussed in this description may practice
the invention as well.
* * * * *